The subject matter herein relates generally to a machine for receiving elongated products mutually attached end to end to form a continuous string of products and performing a manufacturing operation with one or more of the individual products, and more particularly, to a feed mechanism for incrementally feeding the string of products.
Machines for handling continuous strips of elongated products that are mutually attached end to end must be able to intermittently engage and advance each individual product into precise alignment for performing some manufacturing operation without regard to tolerance buildup caused by dimensional variations of the individual pieces of the strip. Typical examples of elongated products that are mutually attached end to end are square wire pins and round wire pins. For example, current products are formed as a strip of individual elongated, adjacent pins which are interconnected or attached end to end at indentations. In one embodiment, the strip of pins is made of square wire so that the pins have a square cross section. In another embodiment, the strip of pins is made of round wire so that the pins have a round cross section. Each indentation includes angled surfaces that are formed on the two adjacent pins. Other types of elongated products may also be fed into machines for further manufacturing.
One prior art feed mechanism includes a block having a track formed therethrough containing and guiding a strip of pins. A feed pawl is pivotally attached within a cutout in the block by means of a pivot pin. The feed pawl is urged by a spring to pivot clockwise so that a point engages an indentation of the strip. As the block is moved in the feed direction, the point is pressed firmly into the indentation forcing the strip against the opposite wall of the track so that the strip must move along with the block. After the end of the feed stroke is reached, the strip is held in place while the block is moved in the return direction. This movement requires that the point cam out of the indentation and ride along the outer surface of the pin until the point reaches the next upper indentation, when the feeding process can be repeated.
A potential problem arises in that, as the point of the feed pawl rides along the surface of the pin the pawl may scratch or otherwise mar the pin. Another potential problem with this prior art mechanism is that the block necessarily moves through a fixed distance during the feed and return strokes. In the event that the longitudinal spacing of the indentations varies or is slightly different than the fixed movement of the block, the amount of the variation can accumulate to the point where the variation exceeds the length of the indentation. This occurs because at the top of each return stroke, the point engages the angled surface wherever the point is positioned and then will feed the strip from that position a fixed amount and then will return to a return position, which may be slightly further away than the fixed return stroke anticipates. Each cycle causes the point of the pawl to engage the angled surface further and further away from the center of the indentation. Eventually, the point may no longer engage an indentation and the feed mechanism will malfunction.
Another known feed mechanism, as shown in U.S. Pat. No. 6,405,915, provides a feed mechanism that feeds a strip of elongated products without scratching or marring the outer surface of the product. The machine includes a frame and is arranged for incrementally feeding the strip of products and performing a manufacturing operation therewith. Each two adjacent products are attached at an indentation. The feed mechanism is coupled to the frame of the machine for incrementally feeding the strip of products. The feed mechanism includes a feed track for closely receiving and guiding the strip of products along a first axis, and first and second feed fingers mutually opposed on opposite sides of the first axis.
A means is provided for moving the first and second feed fingers toward the first axis until in feeding engagement with the strip of products without gripping the strip of products. However, the actuator used for moving the first and second feed fingers in a direction parallel to the first axis thereby feeding the strip of products along the first axis requires excessive time and skill for set up and consequently is costly.